Multiple passes of the signal.
Pavel,
I took your original line level "music2" track and recorded it in the same way, taking the voltage output from across the speakers. Volume was moderately high and I used a 2k2 and 330 ohm divider on each channel to derive a reasonable line level signal. I then kept repeating the process, replaying the recording and re-recording it, over and over... like a copy of a copy of a copy etc and did this 5 times. The levels are a bit variable and I noticed the volume getting a bit lower each time so for the last recording I turned the amp volume back up quite a bit.
You can certainly hear the noise build up on these. Very interesting I think.
https://www.dropbox.com/s/91a05ehgc32ml2c/Music2 chain.wav
https://www.dropbox.com/s/aff5gj36jmw03jr/Music2 chain pass 2.wav
https://www.dropbox.com/s/bpl8041liacy3ft/Music2 chain pass 3.wav
https://www.dropbox.com/s/jo9x14fdf4aatvi/Music2 chain pass 4.wav
https://www.dropbox.com/s/x96dy8n9pucl9gd/Music2 chain pass 5.wav
Pavel,
I took your original line level "music2" track and recorded it in the same way, taking the voltage output from across the speakers. Volume was moderately high and I used a 2k2 and 330 ohm divider on each channel to derive a reasonable line level signal. I then kept repeating the process, replaying the recording and re-recording it, over and over... like a copy of a copy of a copy etc and did this 5 times. The levels are a bit variable and I noticed the volume getting a bit lower each time so for the last recording I turned the amp volume back up quite a bit.
You can certainly hear the noise build up on these. Very interesting I think.
https://www.dropbox.com/s/91a05ehgc32ml2c/Music2 chain.wav
https://www.dropbox.com/s/aff5gj36jmw03jr/Music2 chain pass 2.wav
https://www.dropbox.com/s/bpl8041liacy3ft/Music2 chain pass 3.wav
https://www.dropbox.com/s/jo9x14fdf4aatvi/Music2 chain pass 4.wav
https://www.dropbox.com/s/x96dy8n9pucl9gd/Music2 chain pass 5.wav
Hi Karl, I will try it very soon. It is a great idea, lot of fun. I played my file with maximum RMS output level of about 3Vrms. I wil post a test schematic.
Just tried, all the files start with mid - to - high freq interferences, either ground loops or A/D. The continual degradation is interesting.
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It is quite interesting to compare these two files, by listening:
https://www.dropbox.com/s/7az52pby3ih7ul4/complete_audio_chain.wav
https://www.dropbox.com/s/91a05ehgc32ml2c/Music2 chain.wav
https://www.dropbox.com/s/7az52pby3ih7ul4/complete_audio_chain.wav
https://www.dropbox.com/s/91a05ehgc32ml2c/Music2 chain.wav
That is far more sophisticated than the simple divider chain and commoned grounds of my set up.
I hear the noise on mine. That has to be the Dell A/D soundcard doing that because yours is audibly "silent" on playback via speakers. It seems to resolve better image wise than when I listened earlier, maybe that is just me.Sound quality wise... ooohh... now that's a tough one because I'm replaying yours (and mine) through mine of course. On audition I would say mine is slightly less "up front" but we are talking a matter of degrees, and with slightly less "grip" in the extreme lower bass. On the vocals, well I think on mine there is a certain "presence", the warmth and inflexions come across very well... I listened about 10 times to each... I'm listening again now... depth it has depth, the image resolves behind the speakers... its not just a spread of sound... but again a matter of degree.
Time for tea.
If the load impedance is non-linear, then current is non-linear even if voltage is perfectly linear. But? You will only see you have non-linear load.
These considerations are confusing the issue. We normally deal with speakers that are designed for voltage drive. Then, cleanest voltage drive is best. There is another thread about voltage x current drive, this seems to be a fashion topic now.
These considerations are confusing the issue. We normally deal with speakers that are designed for voltage drive. Then, cleanest voltage drive is best. There is another thread about voltage x current drive, this seems to be a fashion topic now.
Yes the load speaker is nonlinear and so is the amplifier. Some distortion products can be cancelled and some amplified by this union. As mentioned earlier the signs of the polynomial terms are crucial. A nonlinear characterisation of the real amplifier is needed, if the purpose is to compare amplifiers. A Volterra model for example. It's not going to be very easy though.
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Sorry, Karl, this is a solid 'victory',
, for Pavel's chain. Yours has some added character which at times appears to more "interesting", but Pavel's effort is more true to the original. Shows clearly in the expression in the voice, and the little run on the piano towards the end.Would be interesting to do another series of tests, where the volume through the speakers was lifted by, say, 10dB on each take, but the actual recorded volume remained the same, by altering the voltage divider, say. This would assess how the character of the amp alters as the power requirement on it varies - how capable is the power supply, etc ...
^ This is exactly what I was thinking... the higher the drive level, the more likely back emf from the speakers is going to be having an effect on things. So I think for any valid comparisons, we would need to specify what the voltage is at the speaker terminals at say 50 Hz or 100Hz and set that as the reference level.
Obviously this is going to result in quite different spl levels depending on the efficiency of the speakers.
Of course it really only shows us how a particular amp behaves with a particular speaker. Since we all have different speakers, any overall comparison is a bit murky. It is possible for example that if Mooly's speakers were used on Pavels Chain of equipment that the results would be different to with Pavel's speakers.
What the test shows is how two different amps can behave differently for a given source and load, where the only variable is the amp under test. Comparing the results of one persons amp, with different source and speakers (and recording equipment) is not really a valid comparison, but is of course of interest
Tony.
Obviously this is going to result in quite different spl levels depending on the efficiency of the speakers.
Of course it really only shows us how a particular amp behaves with a particular speaker. Since we all have different speakers, any overall comparison is a bit murky. It is possible for example that if Mooly's speakers were used on Pavels Chain of equipment that the results would be different to with Pavel's speakers.
What the test shows is how two different amps can behave differently for a given source and load, where the only variable is the amp under test. Comparing the results of one persons amp, with different source and speakers (and recording equipment) is not really a valid comparison, but is of course of interest
Tony.
Of course. This is the goal of many designers, to be able to have a design that can in some ways be likened to a laboratory amplifier (within its performance envelope) where voltage out is, according to measurement, an exact replica of voltage out. See also my reply to Frank below
Sorry, Karl, this is a solid 'victory',
Would be interesting to do another series of tests, where the volume through the speakers was lifted by, say, 10dB on each take, but the actual recorded volume remained the same, by altering the voltage divider, say. This would assess how the character of the amp alters as the power requirement on it varies - how capable is the power supply, etc ...
Appreciate the comments Frank
So more true to the original !You all want me to be honest in this and with my comments and so here goes.
Pavels amp, amplifiers like the classic blameless of Doug Selfs, even amplifiers like the little Rotel... they all seem to have a common trait to the sound quality. There is a sensation that the speaker is under immense control all the time... and over long term listening it is a sound I find fatiguing. It's a sound I've lived with for many years with both commercial and diy designs, a sound where I kept trying to convince myself it was "right" or "correct" or whatever and yes... in terms of the definition of an amplifier it probably was. For listening enjoyment it wasn't for me though. There is somehow an artificialness to the audio presentation that is ever present... its lacking in being able to present a convincing image that hangs between the speakers, and not just behind but in front and behind too.
So there we are. It all comes down to absolutely total subjectivity at the end of the day.
Karl, I understand where your comments are coming from, and I sympathise with your sentiments. However, and it's a big however , there is green grass on the other side, on the side of achieving the highest levels of accuracy. No pain, no gain is the simplistic expression - and it does fit to some degree in getting the best from audio.
That fatiguing, artificial quality, to 'accurate' sound, is a manifestion of how it often comes across when the sound is 95% on the way to 'being there' - and it will remain so until you hit the 100% marker. Having gone this journey over and over and over again, through many years, I know this well-worn path like the proverbial back of my ...
It's always been worthwhile persisting with accurate sound, because the reward, when it comes, is quite overwhelming, and immensely satisfying!
Just letting you know ...
, there is green grass on the other side, on the side of achieving the highest levels of accuracy. No pain, no gain is the simplistic expression - and it does fit to some degree in getting the best from audio.That fatiguing, artificial quality, to 'accurate' sound, is a manifestion of how it often comes across when the sound is 95% on the way to 'being there' - and it will remain so until you hit the 100% marker. Having gone this journey over and over and over again, through many years, I know this well-worn path like the proverbial back of my ...
It's always been worthwhile persisting with accurate sound, because the reward, when it comes, is quite overwhelming, and immensely satisfying!
Just letting you know ...
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